The person said prosecutors are expected to bring criminal charges soon against both Dr. Salomon Melgen and Menendez. The person insisted on anonymity because the person was not authorized to discuss an ongoing investigation on the record.

The federal investigation has centered on whether the Democratic senator abused his office by taking actions to benefit the doctor, who provided Menendez with flights to and from the Dominican Republic on his luxury jet.

Menendez has repeatedly denied wrongdoing. He says he acted honorably in office.